Means for reducing reflection losses in phantom circuits.



` T. SHAW. 4MEANS POR RBDUC1NG REF LEGTION LOSSES PHANTOM CIRCUITS.

' APPLICA-T10N FILED, 11213.28, 1913.

7 In Ven zoz T. SHAW.- MEANS FOR4 REDUUING REFLBCTION LSSES IN PHANTOM CIRCUITS.

APLICATION FILED IEB.28,1913`.

` Patented Apr. 14, 191.4

2 BHEETS-SHEET 2.

nitirnn THOMAS SHW, OF IELACHENSAK, NEW JERSEY, ASEGNO@ T43 AMERCAN TELEPHOE A AND TELES-RARE COKPANY, A Oitl'ltii'lq Oli' NEVI YORK.

MEANS FOB, REDUCING REFLEEltQlil Lgt-'555323 XN PHANTXVL CIRCUITS.

tenesse.

Specicetioii ci Letters, .'teitcnt.

Patented fini. te, initd..

Application iiled Eebrury 28%, 3.333. Serial. We. 751,288.

To all '107mm 'it may concern Be :it known that l, TiroMAs SHAW, s citizen of the United States, residing at Iaekensack, in. the county of Bergen and State ot New Jersey, have invented certain Improvements in Means for Reducing Re lection Losses in Phantom Circuits, ci which the iiolloii'ing1 is specification.

To decrease the triinsniission losses caused by i'eiiection' et the junction ot telephone lines of diiercnt impedance. a w'eli known expedient consists in connectii'igl these iinc-s through a transformer adapted to step up or down, Vthe ense may he, the iiiipedunee of one line to that of the other, this reticetion reducing' ineans beingniost etiective when the impedance rstio c-tthet rusiforiiier equals the rutio of impedsiices ot the lines.

The present invent-ion hns for its object. certain improvements iii reiection reducing means of this character, it being especially applicable to theft portion of a duplex telephone. circuit termed n4 phantom circuit.

` Because of the greater efficiency over the separate winding' transformer, both with respect to copper and iron losses, of the type of device comn'ionly known as nn nutotranstormer, in which the windings are con* ductively connected, and because ot its inziiiitenanceoi the direct conducthe coiitinuity of the circuits, this device is useful in the present connection and with it my invention :is more specifically concerned.

ln the accompanying drawings, Figure 1 shows diagi'animatically elements oi a phen tom circuit embodying my invention; l. `ig. 2 is u diagrammatic' representation of an autOt-rniisforiiier for use in the phantom circuit; and Fig. 3 is a siiriilur'view ofsucli ziV device adapted for application to the sides of the phantom.

Simi ar characters of reference designate like parts throughout.

In Fig. l isillustrsted a portion ot' :i phantom telephone circuit consisting of ihysieal circuits L1, L2 with the vconductoi.;s 1n parallel furnishing the, sides of the phantom. For the purposes ofthis invention the physical circuits are considered to be in successive sections turnisliedby connected lines or portions of :i single line, these sections presentlngdii'l'erent imperi-ences. rThe phantom would therefor-clinic cth-respondv ing` sections S, S" likewise diiierent in iiniicdiince, S being the low and Sl the high `impedance section. At the junction of these sections reiiection losses naturally occur.

Included in the phantom circuit between the high and low impedance sections is a reilection reducing device preferably con* Sistine; ci. en autotrzinsifornier U. Thewindings 'ci und u?, un, u?, u2 ot this transformer tney ce iooired upon as bea-ring a. bridge and seriesl relation to the phantom. u1 find u nre sel rately in seriesv with the two conductors ot' the side circuit L1, while uf", 'm ilnriy included. in the conductors ed by conductors et L". it is i' c c iiotween neutral points ot the side circuits thrt h e suitniiie'combination of inducteiices and ccpecities, here illustrated in the bridge windings of sutotransfornr ers T1, T2 belonging to the respective4 side circuits '.R., Fh?. ihese deiices T1 and T2, which inlay be it'titicei in construction, wiil be leiter more itt iy described. rihe bridge windingr u, of autotransioriner U having connection with theV side circuits, as z ibove described, is entirely independent of oper sting current in the latter circuits and csirries only operating current for the phantom, this being the difference between the current in the low end high impedance phantom sections. The current in said low impedance section does not traverse the series windings of the autotransformer' U. through which flows the euri-ent in the high impedance section of the phantom, together with the operating; current of the respective side circuits. lt desired 'that the transformer U shrill produce its full. reflection reducing effect upon the phantom circuit without substsntial eti'ect upon the side circuits. To this end the impedance of the bridge of the phantom, which consists mainly of the iinpednnce of the, windingu, should zipproxi- .oi' the coi'npanion pair.

dii'lerent distances from theV core; that is,

one section of each pair is adjacent to the core and the other section outside a section Over the series windings is placed the bridge winding 9--10, also enveloping the whole core and being in sections equally divided between the halves ot' said core. With the elements of the transformer in the relation shown, and considering first the phantom circuit, the series windings of each side circuit are in parallel. with the mutual indu'ctance aiding the inductances; and taken together the Iside circuit windings are in series with the mutual inductance between the pairs aiding'the self inductances. Furthermore, the mutual inductance between the bridge winding and all the series windings increases the total inducta'nce of the trans former for' the phantom. The rellection reduring eliciency ol the device may be ex- `comparatively unimportant.

pressed by the ratio ot the impedance resulting from the series-connection ot the lnidge winding 5)-10Vand the pairs 1 2, Le and stl, THS of series windings in inductirte-aiding relation (it being reinem hered that each oi these pairs of series windings considered separately is in parallel indnctirely aiding) to the impedance of the bridge winding. As the peculiar connection ot' the bridge winding prevents its iniiuencing the side circuits, the only eliect of the transformer upon the -side circuit will be the series opposing impedance of the series windings, which will be equivalent to their direct current resistance only. The careful impedance balance between the varius windings of the transformer practically eliminates electromagnetic crosstalk through it between the phantom and its sides. The twisting of both pairs of series vwindings and the alternating of the sections give. perfeet mutual 'symmetry with respect to the bridge winding, and of course one to the 'other'. As to electrostatic crosstalk, the only direct admittiaees which can cause this and which are u symmetrical are .those Abetween the outer layers of the series windings and inner layersfof the bridge winding. This is By `properly proportioning the various windings of the transformer EU an impedance ratiomay be obtained adapting it to any particular values of impedance ofthe circuit sections. I will give the approximate data for a'transformer such as hereinbefore -described having the ratio of 3 to l. The sections of the bridge winding may have 1,000 turns of conductor with a direct current resistance of 8 ohms; `series 'windings 1-2, li-4c; 5-43, 7 8, each 365 turns with a direct current resistance of 4 ohms. For the phantom circuit there will be introduced by th'e transformer at a frequency of 800 cycles a series impedance of '12+ ohms and 0.493 henry, a bridge impedance of 233 ohms and 0.925 henry and a mutual impedance of 163 ohms and 0.67 henry. For each side circuit there will be a series impedance of 8 ohms and 0.*001 henry.

It is desirable to provide` separate transformers for reducing the reflection losses in each side, these to be without substantial eifect u )on the phantom, in the same manner as the phantom transformer is indepcndent of the sides. The transformers T1, T2,

previously referred4 to as furnishing the inductances through which the bridge winding of the phantom is connected, are preferably thus organized, and one of these will now` be described. rll`his transformer, as T1, comprises sets of windings t andtl, t2, which may conveniently be called the bridge and series windings, respectively. finding t is bridged across'the junctionof the two circuit sections, while the series windings are connected to the .extremities of thebridge in each of ,the conductors of the high impedance section. To allow common battery signaling, and for other purposes in which a metallic bridge is objectionable, the continuity of the bridge winding-is broken by a balanced set of condensers C, C, from between which the connection c to the bridge winding of the phantom transformer U is led. These condensers serve also to break the metallic continuity of the phantom bridge. To practically confine the ellectof -the transformer T-l to its side circuits its windings are arranged as follows, with the terminal connections as particularly indicated b v numerals: A core A (Fig. 3) having a closed l'nagnetic circuit, preferably of toroidal form, is shown. Extending about the cntire core is the bridge windiugt and series windings 1 and t2. rThe winding t is divided into sections between which. condensers C, C are inserted, these sections having terminals 1-`2" and 56. The series winding 151 of one of 'the side conductors has terminals SLA", and the series winding t2 of the other conductor Iterminals If-8. Each series windingrmay be divided into two sections, all .the sections having the same number of. turns. Either the bridge or series windings preferably` consistsof a twisted' ing to'the total inductance of the windings for said phantom circuit.

12. The combination with two physical circuits associated to furnish a phantom circuit,- of a reflection reducing transformer for the phantom circuit vhaving a bridge winding connected between the physical circuits, and series windings in the conductors of the physical circuits.

13. The combination with two physical circuits associated tofurnish a phantom circuit comprising successive sections, of` a transformer situated at the junction of the phantom sections and having a core, and windings on the core consistin of series windings in conductors of the p ysical circuits, and a bridge winding connected between the conductors of the physical circuits, one of the windings being in the form of a twisted pair.

14. rlhe combination with' two physicalv circuits associated to furnish a phantom circuit comprising successive sections, of a transformer situated at the junction of the phantom sections and having a core, and windings'on the core consisting of a series winding` for each conductor ofthe physicalA circuits, and a bridge winding connected between the conductors-of the physical circuits in parallel, they series windings for each physical circuit' being in the form of a twisted pair. y

l5. The combination with two physical 'circuits associated to furnish a phantom Acircit comprising successive sections, of a transformer situated at the junction of the phantom sectionsdand having a core, and windings on the core consisting of a series winding for ea'ch conductor of the physical' circuits, and a bridge winding connected between tlie conductors of the physical circuits in parallel, the series windings of each physical circuit being in sections situated on different portions of the core.

16. The combination with vtwo physical circuits associated to furnish a hantom circuit comprising successive sections, of a transformer situated at the junction of the phantom sections and having a core, and windings on the core consisting of la series winding for each conductor of the physical circuits, and a bridge winding connected between the conductors of the physical circuits in parallel, the series windings of each physical circuit being in the form of a twisted pair arranged in sections upon different portions of the core.

17. The combination with two physical circuits associatedto furnish a phantom circuit comprising successive sections, of a transformer situated at the junction of the phantom sections and having a core, and windings on the' core consisting of a. series winding for each conductor of th'e physical circuits, and a bridgeywinding connected between the 'conductors ofthe physicalfcircuits in parallel, the series windings of each physical circuit bein in sections situated on different portions of the core, the sections ofthe same winding being at dierent distances from the core.

18. The combination with two physical circuits associated to furnish a phantom circuit comprising successive sections, of a transformer situated at the junction of the phantom sections and having a core, and windings on the core consisting of a series winding for each conductor of the physical circuits, and a bridge winding connected be tween the conductors of the physical circuits in parallel, the'series windings for each. physical circuit bein in the form of a twisted pair and the bridge winding being a single conductor located outside the series windings.

19. rilwo physical circuits associated to finnish a phantom circuit, the physical and phantom circuit-s comprising sections of different impedance, and a separate reflection Areducing transformer situated at the junction of the sections of each physical circuit and of the phantom circuit.

20. Tiwo physical circuits associated to furnish a phantom circuit, the physical and phantom circuits comprising sections of dif-v ferent inipedance, a separate reflection reducing transformer situated at the junction of the sections of each physical circuit and of the phantom circuit, and means forming a part ,of each transformer for substantially confining the reflection reducing effect of each transformer to its individual circuit.

21. Twp physical circuits associated to furnish a phantom circuit, the physical and pliantom'fcircuits comprising sections of different impedance, a separate reflection reduciiig transformer situated at .tle junction of the sections of each physical circuit and of the phantom circuit, the windings of each transformer being inductively arranged to substantially confine the effect oi each transformer to itsindividual circuit.

22. Two physical circuits associated to furnish a phantom circuit, the physical and phantom circuits comprising sections of different impedance, a separate reflection reica ducing transformer situated at the junction of the sections of each physical circuit and of the phantom circuit, each transformer having series windings and av bridge winding, the bridge winding of the transformer in the phantom circuit being connected to the bridge windings of both transformers in the physical circuits. i

28. Two physical circuits associated to furnish a phantom circuit, the physical and phantom circuits comprising sections of different impedance, a. separate reflection reducing transformer situated atthe junction ofthe sections of each physical circuit and havinov series windings and a bridge winding, the bridge Winding of the transformer day of February, 1913.

in the phantom circuit being Connected t0 the bridge windings 0i both transformers in the physical cireuitsfat'neutral points therein.

In ltestimonywhereof, I have signedmy of the phnntmn circuit, each transformer name to this specification in the` presence of two subscribing Witnesses., this eighteenth w THOMAS SHAW.

Witnesses:

ELAM MILLER, LLOYD EsPENsemnn. 

